This invention relates generally to equipment utilized for the testing of electrical components, and, more particularly to a test station capable of probing the surface of semiconductive devices while the devices are in the actual atmosphere and at the actual temperature at which they are to be used.
The use of probes to electrically assess semiconductor devices is an established practice in semiconductor technology. Probing of devices prior to commiting them to attachment of permanent electrical leads allows one to reject those devices which do not meet certain established specifications. Heretofore, the devices to be tested were generally tested at ambient temperature and in normal atmosphere. In other instances, the testing procedure required that electrical contacts be bonded to the device and that the device be immersed in a cryogenic fluid such as liquid nitrogen, for testing at the temperature of the liquid. Such procedures, generally, produced results which were unsatisfactory.
Since the advent of new semiconductor technologies, it is now extremely important to probe electronic devices in vacuum or reduced pressures and at cryogenic temperatures. Furthermore, testing is now required of integrated arrays of infrared photovoltaic semiconductor detectors, such as those constructed of the alloys of PbSnTe and InAsSb. In these cases, it is necessary to cool the devices to as low as 30.degree. K., although useful measurements can sometimes be made at temperatures as high as 195.degree. K. The situation is further complicated since these new materials, because there are very large arrays of individual detectors on one chip, must often be probed. These arrays may contain from one to several thousand detectors. Therefore, the probes must be capable of moving to each detector. Because of the large number of detectors, it is impractical to connect a wire to each detector for testing as accomplished in the past.